Oceanic Whitetip Sharks, Carcharhinus longimanus, are a species of shark feared by many. Along with Great Whites, Bull Sharks, Makos, and Tiger sharks, Oceanic Whitetips are labeled as one of the most dangerous sharks in the ocean.
There are multiple stories of shipwrecked crew members being surrounded and picked off by Oceanic Whitetip Sharks, but only 5 confirmed bites have been recorded since 2009. Once one of the most common species found in the ocean, their population has been decimated, with some areas retaining less than 1% of their original population. That’s a loss of more than 99% of Oceanic Whitetip Sharks in a specific area.
Habitat/Distribution
Oceanic Whitetip Sharks are a pelagic species of shark found in tropical and subtropical oceans. They are found worldwide in the open ocean, on the outer continental shelf, and around oceanic islands with deep surrounding waters.
Image courtesy of carnivora.net
They have a preference for water temperatures between 20°C and 28°C (68-82°F) and are commonly found in the upper water column near the surface. They are generally thought to be surface-dwelling sharks but have been known to swim for extended periods at depths reaching 150 meters (almost 500 feet).
Diet
Oceanic Whitetip Sharks are usually solitary. They cover large distances in search of food and are opportunistic eaters, meaning they will eat just about anything if they are hungry enough. They prefer to feed on body fish and cephalopods (especially squid) but will also feed on large pelagic sportfish like marlin and tuna, other sharks and rays, birds, marine mammals and even trash floating in the water if resources are low.
When food is plentiful, these sharks will get into feeding frenzies. This generally happens when sharks are overwhelmed with the amount of prey available and there are multiple sharks in one area. They will fight for their share of food, often biting each other and whatever else is around them in their excitement.
Description
Oceanic Whitetip Sharks are an easy species to identify. They are named after the prominent white markings on the tips of their dorsal, pectoral, and tail fins. Unlike the similarly named Whitetip Reef Shark, they have distinctly rounded, paddle-like fins, and are found in the open ocean rather than coral reefs.
Image courtesy of NOAA
Other defining characteristics include:
- Large, stocky bodies with a bluntly rounded snout
- Their powerful jaws and fins are larger than most other shark species.
- The lower jaw has small, thin, triangular teeth with serrated tips while the upper jaw has broader teeth that are entirely serrated.
- Their body color changes slightly depending on geographic location, and can be shades of brown, grey, beige, or sometimes bluish on top, with a white underbelly.
- They have circular eyes and nictitating membranes they use to help them protect their eyes when hunting/eating.
- Most grow to about 3 meters in length with the largest ever recorded being 4 meters.
Image courtesy of The Ecologist
Reproduction/Lifespan
Oceanic Whitetip Sharks are long living, late to sexual maturity, and have low to moderate litter sizes, making them especially susceptible to population decline.
This species of shark generally lives up to 25 years, but some accounts have been shown of individuals much older. Females reach sexual maturity between 6 and 9 years of age depending on geographic location.
Image courtesy of ScienceDirect
They are viviparous, giving birth to live pups, after a gestation period of 10 to 12 months. Their reproductive cycle is thought to be biennial. This means they give birth on alternate years, taking a break in between litters. Litter sizes range anywhere from 1 to 15 pups, with a possible correlation between female size and litter size.
Nurseries have not been discovered yet, but young juvenile Oceanic Whitetip Sharks have been found in open waters close to the southeastern part of the United States.
Threats
The Oceanic Whitetip Shark is one species whose population has been especially devastated by commercial fishing and the shark fin trade. Being a species that is commonly found in the upper water column of open ocean they are frequently caught in gillnets, pelagic longline, purse seines, and targeted specially for their highly valued white tipped fins.
Once an abundant and commonly shark found in the ocean, the Oceanic Whitetip Shark’s population has declined by appx. 80 to 95% across the Pacific Ocean since the mid-1990s. Studies done, focusing on the Gulf of Mexico have estimated a decline in population size by an estimate of 99.3% from the mid-1950s to late-1990s.
The Oceanic Whitetip was added to the IUCN Red List in 2019 as Critically Endangered due to drastic declines in reported catch quantities.
Image courtesy of IUCN Red List
Bonus Facts:
- Though usually solitary, these sharks have been seen forming unusual associations with Shortfin Pilot Whales of the coast of Hawaiian waters. These whales have an impressive ability to locate squid, and it is thought that this relationship formed as a source for Oceanic Whitetips to locate one of their favorite prey.
- Like Great Whites, Oceanic Whitetip Sharks rely on ram ventilation in order to breath. Unlike other sharks that are able to pump water over their gills, they have to keep in constant motion so the oxygen in the water can wash over their gills, allowing them to breath.